U.S. patent number 7,016,159 [Application Number 10/201,834] was granted by the patent office on 2006-03-21 for disk drive head suspension with spring rails for base plate microactuation.
This patent grant is currently assigned to Hutchinson Technology Incorporated. Invention is credited to Jacob D. Bjorstrom, Reid C. Danielson.
United States Patent |
7,016,159 |
Bjorstrom , et al. |
March 21, 2006 |
Disk drive head suspension with spring rails for base plate
microactuation
Abstract
A base plate for a head suspension assembly having a pair of
side rails including spring portions. The base plate including
first and second portions connected by the pair of side rails and
separated by an opening, with the spring portions positioned
adjacent to the opening. The base plate configured to receive a
microactuator spanning the opening with the microactuator causing
relative movement between the first and second portions of the base
plate at the spring portions of the side rails, so as to provide
fine manipulation of a head slider mounted to the head suspension
assembly.
Inventors: |
Bjorstrom; Jacob D. (Waconia,
MN), Danielson; Reid C. (Cokato, MN) |
Assignee: |
Hutchinson Technology
Incorporated (Hutchinson, MN)
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Family
ID: |
36045605 |
Appl.
No.: |
10/201,834 |
Filed: |
July 24, 2002 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
Issue Date |
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60307448 |
Jul 24, 2001 |
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Current U.S.
Class: |
360/294.6;
G9B/5.153; G9B/5.193; G9B/5.197 |
Current CPC
Class: |
G11B
5/4833 (20130101); G11B 5/5552 (20130101); G11B
5/5569 (20130101) |
Current International
Class: |
G11B
5/55 (20060101) |
Field of
Search: |
;360/294.6,294.4 |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
Other References
Excerpts from Magnecomp presentation at "Head/Media Las Vegas '99
Proceedings" 2 pgs. cited by other.
|
Primary Examiner: Castro; Angel
Attorney, Agent or Firm: Faegre & Benson LLP
Parent Case Text
The present application claims priority to U.S. provisional
application Ser. No. 60/307,448, entitled DISK DRIVE HEAD
SUSPENSION WITH SPRING RAILS FOR BASE PLATE MICROACTUATION, filed
on Jul. 24, 2001, which is herein incorporated by reference in its
entirety.
Claims
The invention claimed is:
1. A head suspension assembly for supporting a head slider in a
rigid disk drive, the head suspension assembly comprising: a load
beam having a proximal end, a distal end, and a spring region
having a thickness; and a base plate coupled to the load beam at
the proximal end, the base plate including first and second
portions having thicknesses greater than the thickness of the load
beam spring region and joined by a pair of side rails extending out
of a plane of the base plate, the side rails providing for relative
motion between the first and second portions of the base plate.
2. The head suspension assembly of claim 1, wherein each side rail
is integrally formed in the base plate of base plate material.
3. The head suspension assembly of claim 1, wherein each side rail
includes a spring portion positioned adjacent to an opening formed
between the first and second portions of the base plate, and
wherein the relative motion of the base plate includes actuation of
the spring portions.
4. The head suspension assembly of claim 3, further comprising a
microactuator mounted to the base plate and positioned to span the
base plate opening for providing relative movement between the
first and second portions.
5. The head suspension assembly of claim 3, wherein each spring
portion comprises a configuration selected from the group
consisting of `V` shape, `U` shape, `S` shape, square, rectangular,
sinusoidal, corrugated and accordion pleated.
6. The head suspension assembly of claim 3, wherein the pair of
spring portions are symmetrically configured about a longitudinal
axis of the head suspension assembly.
7. The head suspension assembly of claim 3, wherein each spring
portion protrudes outwardly from an edge of the base plate in a
direction away from the base plate opening.
8. The head suspension assembly of claim 3, wherein each spring
portion protrudes inwardly from an edge of the base plate in a
direction toward the base plate opening.
9. The head suspension assembly of claim 1, further comprising a
flexure at the distal end of the load beam, the flexure configured
to support a head slider.
10. The head suspension assembly of claim 1, wherein the pair of
side rails are each substantially perpendicular to the plane of the
base plate.
11. The head suspension assembly of claim 1, wherein the pair of
side rails extend away from the plane of the base plate on a side
of the base plate on which a flexure is located.
12. The head suspension assembly of claim 1, wherein the pair of
side rails extend away from the plane of the base plate on a side
of the base plate opposite the side on which a flexure is
located.
13. The head suspension assembly of claim 1, wherein the first
portion comprises a drive mounting region and the second portion
comprises a load beam mounting region separated from the drive
mounting region by the base plate opening, the load beam mounting
region integrally connected to the drive mounting region by the
pair of side rails and the load beam mounting; region coupled to
the load beam.
14. The head suspension assembly of claim 13, wherein the drive
mounting region comprises a boss for attachment of the head
suspension assembly to an actuator arm of the disk drive.
15. The head suspension assembly of claim 1, wherein the first
portion of the base plate is configured for attachment to a primary
actuator of the disk drive and wherein the second portion of the
base plate is attached to the load beam proximal end.
16. The head suspension assembly of claim 15, wherein the first
portion of the base plate includes a swaging boss tower for
attachment to a primary actuator.
17. The head suspension assembly of claim 15, wherein the head
suspension assembly further includes welds for attaching the load
beam proximal end to the second portion of the base plate.
18. The head suspension assembly of claim 1, wherein the base plate
comprises one piece of material.
19. The head suspension assembly of claim 1, wherein the base plate
comprises one piece of material and the first portion, second
portion, and side rails all have a thickness greater than a
thickness of the load beam.
20. A base plate for use in connection with a disk drive head
suspension including a spring region having a thickness, the base
plate comprising a pair of rails extending out of a plane of the
base plate and bounding a base plate opening and having a thickness
greater than the head suspension spring region thickness.
21. The base plate of claim 20, further comprising a drive mounting
region and a load beam mounting region separated from the drive
mounting region by the base plate opening, with the load beam
mounting region connected to the drive mounting region by the pair
of rails.
22. The base plate of claim 21, wherein the pair of rails are
integrally formed in the base plate of base plate material.
23. The base plate of claim 20, wherein each rail includes a spring
portion adjacent to the base plate opening.
24. The bast plate of claim 23, further comprising a microactuator
mounted to the base plate and positioned to span the base plate
opening, the microactuator configured to provide fine movement of
the head slider mounted to head suspension assembly by causing
longitudinal expansion and contraction of the base plate at the
spring portions of the pair of rails.
25. The base plate of claim 23, wherein each spring portion
comprises a configuration selected from the group consisting of `V`
shape, `U` shape, `S` shape, square, rectangular, sinusoidal,
corrugated and accordion pleated.
26. The base plate of claim 23, wherein the pair of spring portions
are symmetrically configured about a longitudinal axis of the base
plate.
27. The base plate of claim 23, wherein each spring portion
protrudes outwardly from an edge of the base plate in a direction
away from the base plate opening.
28. The base plate of claim 23, wherein each spring portion
protrudes inwardly from an edge of the base plate in a direction
toward the base plate opening.
29. The base plate of claim 20, wherein the pair of rails are each
substantially perpendicular to the plane of the base plate.
30. The base plate of claim 20, wherein the pair of rails extend
away from the plane of the base plate on a side of the base plate
on which a flexure is located.
31. The base plate of claim 20, wherein the pair of rails extend
away from the plane of the base plate on a side of the base plate
opposite the side on which a flexure is located.
32. The base plate of claim 20, wherein the base plate includes a
first portion adapted for attachment to a primary actuator of the
disk drive and a second portion adapted for attachment to a load
beam, and wherein the rails provide for transverse movement between
the first and second portions.
33. The base plate of claim 32, wherein the first portion of the
base plate includes a swaging boss tower for attachment to a
primary actuator.
34. The base plate of claim 32, wherein the second portion of the
base plate is adapted for welding attachment to a load beam.
35. A method of forming a base plate having spring rails, the
method comprising the steps of: providing a planar base plate
portion for use in connection with a disk drive head suspension
including a spring region having a thickness, including an opening
surrounded by base plate material and a spring portion in the base
plate material adjacent to the opening and having a thickness
greater than the head suspension spring region thickness; and
forming spring rails from the spring portion adjacent to the
opening, the spring rails formed out of the plane of the base
plate.
36. The method of claim 35, wherein the step of providing a spring
portion comprises forming the spring portion by decreasing a size
of the opening.
37. The method of claim 36, wherein the step of forming the spring
portion comprises forcing the base plate material adjacent the
opening in a direction generally perpendicular to the plane of the
base plate.
38. The method of claim 36, wherein the step of forming the spring
portion comprises forming a pair of spring portions flanking the
opening.
39. The method of claim 36, wherein the spring portion comprises a
configuration selected from the group consisting of `V` shape, `U`
shape, `S` shape, square, rectangular, sinusoidal, corrugated and
accordion pleated.
40. The method of claim 35, wherein the spring rails are
substantially perpendicular to the plane of the base plate.
41. The method of claim 35, wherein the step of forming the spring
rails comprises bending the base plate material adjacent the
opening.
42. The method of claim 35, further comprising the step of mounting
a microactuator to the base plate so as to span the opening.
43. The method of claim 35, further comprising the step of mounting
a load beam to the base plate so as to produce a head suspension
assembly.
44. The method of claim 35, further including forming a swaging
boss tower in the base plate portion.
Description
BACKGROUND OF THE INVENTION
In a dynamic rigid disk storage device, a rotating disk is employed
to store information. Rigid disk storage devices typically include
a frame to provide attachment points and orientation for other
components, and a spindle motor mounted to the frame for rotating
the disk. A read/write head is formed on a "head slider" for
writing and reading data to and from the disk surface. The head
slider is supported and properly oriented in relationship to the
disk by a head suspension that provides both the force and
compliance necessary for proper head slider operation. As the disk
in the storage device rotates beneath the head slider and head
suspension, the air above the disk also rotates, thus creating an
air bearing which acts with an aerodynamic design of the head
slider to create a lift force on the head slider. The lift force is
counteracted by a spring force of the head suspension, thus
positioning the head slider at a desired height and alignment above
the disk which is referred to as the "fly height."
Head suspensions for rigid disk drives typically include a base
plate, load beam and a flexure. The base plate provides a
connection between the suspension and the primary actuator of the
disk drive and may be a swage plate type base plate that mounts via
swaging to member driven by an actuator. Alternatively, the base
plate may be a unamount style arm that mounts directly to the
actuator. The load beam typically includes a mounting region at its
proximal end for mounting the head suspension to an actuator of the
disk drive, typically at a base plate of the head suspension. The
load beam also includes a rigid region and a spring region between
the mounting region and the rigid region for providing a spring
force to counteract the aerodynamic lift force generated on the
head slider during the drive operation as described above. The
flexure typically includes a gimbal region having a slider mounting
surface where the head slider is mounted. The gimbal region is
resiliently moveable with respect to the remainder of the flexure
in response to the aerodynamic forces generated by the air bearing.
The gimbal region permits the head slider to move in pitch and roll
directions to follow disk surface fluctuations.
In one type of head suspension the flexure is formed as a separate
piece having a load beam mounting region which is rigidly mounted
to the distal end of the load beam using conventional methods such
as spot welds. Head suspensions of this type typically include a
load point dimple formed in either the load beam or the gimbal
region of the flexure. The load point dimple transfers portions of
the load generated by the spring region of the load beam, or gram
load, to the flexure, provides clearance between the flexure and
the load beam, and functions as a point about which the head slider
can gimbal in pitch and roll directions to follow fluctuations in
the disk surface.
Disk drive manufacturers continue to develop smaller yet higher
storage capacity drives. Storage capacity increases are achieved in
part by increasing the density of the information tracks on the
disks (i.e., by using narrower and/or more closely spaced tracks).
As track density increases, however, it becomes increasingly
difficult for the motor and servo control system to quickly and
accurately position the read/write head over the desired track.
Attempts to improve this situation have included the provision of
another orsecondary actuator or actuators, such as a piezoelectric,
electrostatic or electromagnetic microactuator or fine tracking
motor, mounted on the head suspension itself. These types of
actuators are also known as second-stage microactuation devices and
may be located at the base plate, the load beam or on the
flexure.
The need for slight but controlled positional adjustments of a head
slider on a disk drive head suspension during operation of the disk
drive is becoming increasingly necessary due to trends in the
industry. Various methods of providing such positional adjustment
have been proposed. As stated above, one such method includes the
use of microactuators, such as piezoelectric elements, on disk
drive head suspensions to provide on-the-fly positional adjustments
to the head suspension and head slider. Within this area of
microactuated head suspensions, there is a need to improve actuator
stroke while still achieving high resonance frequencies and low
motor gram share in the head suspensions. Motor gram share is the
amount of force from the gram load that is transmitted through the
microactuators. Ideally, this gram share force is zero, but in
actuality some force is usually present. There is also a need to be
able to accommodate windage requirements in the load beam while
achieving increased stroke values.
SUMMARY OF THE INVENTION
The present invention provides a base plate for use in a head
suspension assembly that supports a head slider over a disk in a
disk drive. The base plate includes a pair of side rails formed
with spring portions positioned adjacent to an opening in the base
plate. The base plate is configured to received a microactuator
spanning the opening, with the microactuator controlling fine
motion of the head slider by manipulation of the base plate
facilitated by the side rails.
The side rails are preferably formed integrally with the base plate
out of the base plate material. The side rails extend out of the
plane of the base plate, preferably substantially perpendicular to
the plane of the base plate. The spring portions may be formed in
many shapes or configurations, including but not limited to `V`
shape, `U` shape, `S` shape, square, rectangular, sinusoidal,
corrugated and accordion pleated. The spring portions extend inward
toward the opening or outward away from the opening. In one
embodiment, the base plate including a drive mounting region and a
load beam mounting region separated by the opening and joined by
the side rails.
The present invention also provides a head suspension assembly
including a base plate of the present invention. The head
suspension assembly also includes a load beam mounted to the load
beam mounting region, with the load beam including a flexure formed
with the load beam or attached to the load beam. A microactuator
mounted to the base plate spanning the opening controls movement of
the flexure and thus a head slider mounted to the flexure.
The present invention also provides a method for forming a base
plate of the present invention, including the steps of providing a
planar base plate portion having an opening, forming a spring
portion in the base plate material adjacent to the opening and
forming side rails from the base plate material having the spring
portion. In one embodiment, the base plate material is bent in a
direction away from the plane of the base plate to form the spring
portion. The spring portion material is then bent again toward the
base plate to form the side rails.
BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS
FIG. 1 is a perspective view of a head suspension assembly,
including a base plate in accordance with the present
invention.
FIG. 2 is a cross-sectional view of the head suspension assembly
taken along Line 2--2 of FIG. 1.
FIG. 3 is a top view of one embodiment of a base plate, in
accordance with the present invention, in a preliminary form prior
to fabrication of the final base plate configuration.
FIG. 4 is a top view of the base plate of FIG. 3, after fabrication
into the final base plate configuration.
FIG. 5 is a perspective view of a head suspension assembly
including a base plate in accordance with an alternative embodiment
of the present invention.
DETAILED DESCRIPTION
With reference to the attached Figures, it is to be understood that
like components are labeled with like numerals throughout the
several Figures. Referring now to FIGS. 1 and 2, a head suspension
assembly 10 including a flexure 20, a load beam 30 and a base plate
40, is shown. In this embodiment, the base plate 40 includes a
drive mounting region 42 and a load beam mounting region 44, which
are connected by side rails 50, and a bore 41 for mounting to the
head suspension drive or actuator. The load beam 30 mounts to the
load beam mounting region 44 at a load beam mount 32 that may
function as a separate spring region. As used herein, the term base
plate refers to any member providing a connection between the
suspension and a primary actuator for the disk drive. Although
shown as a swage plate type base plate, it is to be understood that
a unamount-style arm or other suitable member may also be used in
the present invention and are included within use of the term base
plate.
Between the load beam mounting region 44 and the drive mounting
region 42 is an opening 46 bounded by the side rails 50. A pair of
microactuators 60 are positioned to span the opening 46 by mounting
at a first end 62 to the drive mounting region 42 and at a second
end 64 to the load beam mounting region 44. The microactuators 60
are preferably piezoelectric motors, but may be any suitable
actuation motor or device capable of causing movement of the load
beam mounting region 44 with respect to the drive mounting region
42. Although shown in this embodiment as a pair of devices, the
microactuators 60 may be a single device or may be more than two
devices, as needed depending on the type of device provided and the
type of movement desired.
In this embodiment, there is no center strut or other structural
portion which spans the opening 46 between the microactuators 60,
as is typically present in other prior art microactuated head
suspension designs. As a result, the microactuators can determine
the pivot point about which the movement of the head slider is
made. Actuation of only one microactuator 60 can allow for very
fine adjustments of the head slider position. Actuation of both
microactuators 60 at the same time can provide for larger
displacements of the head slider. The resulting movement of the
head slider is generally lateral with a slight rotational
component. This rotational component is amplified by the length of
the load beam. The base plate 40 serves as a microactuator linkage
having first and second members joined together by rails that
provide for transverse movement between the these members, thereby
resulting in movement of the head slider.
Referring now also to FIGS. 3 and 4, the side rails 50 are an
integral part of the base plate 40 in the embodiment shown, and are
formed from the base plate 40 to be substantially perpendicular to
the plane of the base plate 40. As shown in FIG. 3, the base plate
40 can be formed from a single, relatively planar portion of
material. In one embodiment, the material is preferably stainless
steel having a thickness of about 0.2 millimeters(about 0.008
inches). This thickness will depend generally on the gram load of
the head suspension and the mass of the load beam. Generally, a
material thickness of about 0.010 inches is the preferred maximum,
but thinner materials are preferred. In this preformed state, the
opening 46 is longer in the longitudinal direction than it is in
the formed state. The side rails 50 are formed by bending of the
side rail material 50 at fold lines 57 out of the plane of the base
plate 40 to form a spring portions 52, shown in this embodiment as
a `V` bend. In one embodiment, each spring portion `V` bend 52 has
an inside angle 58 of about 70 degrees. Formation of the spring
portions 52 at lines 57 result in additional rail bends 53 at fold
lines 59.
As the side rail material 50 is bent to form the spring portions
52, the load beam mounting region 44 moves longitudinally closer to
the drive mounting region 42, thereby causing the opening 46 to
become narrower in the longitudinal direction, but maintaining the
area bounded by the side rails 50. Although shown in this
embodiment as a `V` shape, it is to be understood that the spring
portion 52 may be formed in any of a number of different shapes
that provide a suitable spring characteristic to the side rails 50.
These shapes include, but are not limited to, a `U` shape, a
corrugated shape, a non-symmetrical `V` shape, a square or
rectangular shape, or other suitable configuration.
Preferably after the side rail material 50 is formed to include the
spring portion 52, the side rail material 50 is bent out of the
plane of the base plate 40 at fold lines 55. As a result, the side
rails 50 are then substantially perpendicular to the plane of the
base plate 40, as shown in FIG. 2, having a rail height 51 of about
0.5 millimeters (about 0.02 inches), in one embodiment. However,
this rail height 51 may differ to meet space requirements or for
other design or structural purposes, and may range from about 0.025
inches (about 0.64 millimeters) down to about 0.008 inches (about
0.20 millimeters) for thinner base plates, although other ranges of
rail height are possible. After forming, the single piece base
plate 40 in this embodiment is configured as shown in FIG. 4, with
the side rails 50 having a `V` bend spring portion 52 positioned to
span the opening 46. Each side rail 50 includes a first rail
portion 54 adjacent to the drive mounting region 42 and second rail
portion 56 adjacent to the load beam mounting region 44. Each `V`
bend spring portion 52 protrudes outwardly away from the base plate
40 in a plane substantially parallel to the plane of the base plate
40. Although shown to protrude outwardly relative to the base plate
40, the spring portion 52 of the side rails 50 may be formed to
protrude inwardly, if desired.
The `V` bend spring portions 52 function as springs when the
microactuators 60 are activated. Provision of the spring portions
52 in the side rails 50 results in an increased amount of stroke or
slider movement due to the actuation of the microactuators 60. In
one embodiment, the stroke can provide about .+-.1 micrometer or
more of movement at the head slider.
In general, head suspensions having microactuators mounted on the
load beam, or on a planar base plate, are not capable of producing
both high resonant frequencies and high stroke simultaneously.
Modifications of a planar base plate in order to reduce stiffness
and achieve high stroke usually result in a degradation in the
resonance performance and a corresponding frequency drop. In the
present invention, however, placement of the microactuators 60 onto
the relatively thick base plate 40 (verses the relatively thin load
beam 30) results in a reduction in the effect of the microactuators
60 on resonant frequencies of the head suspension assembly 10. As a
result, relatively high resonant frequencies with relatively high
stroke values are possible. In one embodiment, a stroke value of
.+-.1.23 micrometers can be achieved at a sway frequency of 10.6
kilohertz, and in another embodiment, a stroke value of .+-.0.92
micrometers can be achieved at a sway frequency of 15.5 kilohertz.
The relatively vertical side rails 50 also help increase the
stiffness of the base plate 40, thereby improving resonant
frequencies of the head suspension assembly 10. Increases in the
resonant frequencies have the further beneficial effect of
reducing, and preferably minimizing, windage effects.
Mounting of the microactuators 60 to the thicker base plate 40 also
improves the gram share through the microactuators 60 by reducing
the gram share to about less than one percent. Although elimination
of gram share is theoretically preferred, in practice, reducing
this force to the lowest amount possible is best for the head
suspension assembly 10 and the microactuators 60.
The present invention provides a base plate and a head suspension
assembly including a base plate. The head suspension assembly may
also have a flexure and a load beam to which the flexure is mounted
on one end and to which the base plate is mounted on the other
end.
The base plate includes a pair of side rails that are preferably
integrally formed from the base plate out of the plane of the base
plate, and bounding an opening formed within the base plate. The
side rails each include a spring portion adjacent the opening.
Mounted to the base plate and positioned to span the opening is at
least one microactuator configured to provide fine movement of the
a head slider mounted to the flexure at a distal end by causing
longitudinal expansion and/or contraction of the base plate at the
spring portions of the side rails. Movement of the head slider has
both lateral and slight rotational components.
The side rails may be configured to be substantially perpendicular
to the plane of the base plate. The side rails may also be
configured to extend from the plane of the base plate on the side
away from the flexure, or may extend from the plane of the base
plate on the side of the flexure (as shown in FIG. 5). The spring
portions may have a `V` shape (symmetrical or nonsymmetrical), `U`
shape, corrugated or accordion shape, square or rectangular shape
or other suitable shape. The spring portions may be configured to
protrude outwardly away from the base plate or inwardly toward the
base plate, in a plane substantially parallel to the plane of the
base plate. In addition, the spring portions may be formed to be
symmetrical about a longitudinal axis of the head suspension
assembly.
The base plate may be configured to include a drive mounting region
and a load beam mounting region separated by the opening in the
base plate and integrally connected by the side rails. The load
beam mounts to the load beam mounting region and the drive mounting
region includes a boss for connection to the actuator arm of the
disk drive.
The invention also includes a method for forming a base plate of
the present invention. The method includes the step of providing a
base plate portion including an opening bounded by base plate
material. Another step includes forming a spring portion in the
base plate material adjacent the opening, which may result in a
decrease in the size of the opening. Yet another step includes
forming side rails from the base plate material adjacent the
opening, with the side rails being out of plane relative to the
plane of the base plate and preferably substantially perpendicular
to the plane of the base plate. Even yet another step includes
mounting a load beam to the base plate having the side rails that
include the integrally formed spring portions. A further step
includes mounting at least one microactuator to the base plate with
the microactuator positioned to span the opening.
The step of forming the spring portion may include bending the base
plate material to form a `V` shape (symmetric or non-symmetric), a
`U` shape, an accordion or corrugated shape, a square or
rectangular shape or other suitable shape. The step of forming the
side rails may include bending the base plate material to be
substantially perpendicular to the plane of the base plate.
* * * * *